1. Field of the Invention
The present invention relates to an improved apparatus for effecting gas-tight communications between first and second members having bores for the passage of fluid. More particularly, the present invention relates to an improved connection having a monolithic sealing element with distinct ferrule forming and ferrule biasing engagement surfaces for connecting first and second tubular members.
2. Description of the Background
There are numerous types of analytical instrumentation used in laboratories, chemical and refining plants and the like, which require high temperature connection of a first tubular member through which is transported a fluid, such as a gas, to a second tubular member.
Exemplary examples of such connections are shown in U.S. Pat. No. 4,991,883 ('883) and U.S. Pat. No. 5,163,722 ('722) to R. D. Worden, which are incorporated herein by reference. The connection shown in the '883 patent provides a fluid tight connection for operation over wide temperature ranges and high temperatures that subject the mechanical components of this connection to considerable expansion and contraction. In a preferred embodiment of the invention disclosed in the '883 patent, a fused quartz spring is used as a biasing element to maintain a constant biasing force on a sealing ferrule. The sealing ferrule seals between an inner conduit containing a fluid and an outer sealing surface.
On occasion, it is desirable to use a fluid carrying conduit that is undersize with respect to the sealing ferrule. While a quartz spring provides ample force to maintain sealing pressure during wide temperature variations, such a spring may not be strong enough to make an initial seal with an undersize conduit. The 722' patent shows an apparatus that creates an initial seal by applying force to a follower. After forming an initial seal, pressure is maintained against the follower by the quartz spring.
A continuing problem with high temperature connectors of the type under consideration is the high cost and fragile nature of components often associated with such connectors. The connectors operate at high temperatures in excess of 400.degree. C. They also experience wide temperature swings in excess of 600.degree. C. Additionally, they must be chemically inert to be of practical value. Thus, fused quartz is often the only practical material of which the base portion of these connectors can be formed. However, fused quartz is relatively fragile as compared with steel, for instance. Moreover, fused quartz structures tend to be expensive. While fused quartz is generally impervious to most materials, at the temperatures of operation the fused quartz exposed surfaces may become coated or fused with other materials, e.g., the components passing through the tubular member. When damage of any type occurs, the relatively expensive connector must be replaced. It is frequently necessary to heat the quartz components thereby requiring substantial time and heat energy to bring the structure to the desired temperature and maintain or alter the temperature thereof as required.
Consequently, a need exists for improvements in high temperature connections that experience wide variations temperatures. Those skilled in the art have long sought and will appreciate the novel features of the present invention that solves these problems.